JPMorgan CEO Jamie Dimon told his employees that he has 'curable' throat cancer.

In a note to staff, Dimon said, "The good news is that the prognosis from my doctors is excellent, the cancer was caught quickly, and my condition is curable."

In after-hours trading, the bank's shares slid 0.7 percent after the news.

JPMorgan's board of directors has been briefed on his condition, which will likely call for about eight weeks of radiation and chemotherapy at Memorial Sloan Kettering in New York City, according to the note. The cancer is believed to be contained in Dimon's throat and lymph nodes on his right side.

"I feel very good now and will let all of you know if my health situation changes," Dimon's note said.

Dimon has been CEO of the bank since December 2005, and added the chairman title in December 2006.

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Jamie Dimon

While the prognosis for Dimon's recovery from throat cancer is good, the board does have a short, medium and long terms succession plan in place, a source tells CNBC. Indicating a one- to three-year period, the source says the primary candidates would likely be Gordon Smith, who runs the consumer business; Mary Erdoes, who runs the asset management business; and Daniel Pinto, who runs the investment bank.

Often considered the most powerful CEO on Wall Street, Dimon is known for being blunt, a nod to his Queens roots. The son of a broker himself, Dimon was best known for a time as a star protege of Citigroup's Sandy Weill.

He earned his own acclaim running JPMorgan, particularly during the financial crisis, when his bank stood on firmer ground than many of its struggling peers.

But his reputation was badly damaged by the "London Whale" scandal, a trading blunder out of the firm's chief investment office that cost JPMorgan billions of dollars and led to calls for Dimon's ouster.

He was particularly vilified for dismissing the issue as a "tempest in a teapot" before realizing the extent of the losses.